Figure 4.

Reduced mutator mouse reproduction. (A) Live offspring per mating, plotted against the number of generations; red, mutator mice; blue, control; dots, individual mice; circles, mean for the generation. Solid lines show linear fit and dashed lines show the 95% CI, assuming a negative binomial distribution; green line, regression curve using the recessive lethal mutation model for the mutator lines. (B) The Itga8-mutant genotype in mutD; squares, males; circles, females; filled, homozygotes (but not present here); half-filled, heterozygotes; empty, no Itga8 mutation; and dashed-line circles, post-natal deaths. (×) Failure to reproduce. In 26 tested offspring obtained from the heterozygous intercross, there were no homozygotes (6.5 homozygotes would be expected for a neutral mutation, χ2-test; P < 0.01), indicating that this mutation had a recessive lethal effect on the phenotype.